1. Field of Invention
The present invention relates to controllable power-line-operated inverter-type power supplies for incandesent lamps.
2. Description of Prior Art
Power-line-operated inverter-type power supplies are presently being used in a variety of applications. For instance, such power supplies are frequently being used for powering low-voltage incandescent lamps.
When using such inverter-type power supplies in connection with powering various loads, such as low-voltage incandescent lamps or microwave magnetrons, it is sometimes desirable to be able by way of electrically actuatable means to control the inverter output voltage, thereby providing for control of the power provided to the load. However, to provide cost-effectively for electrically actuatable means to effect control of the output of inverters is not as simple as it might initially appear.
Of course, to achieve such control, one might use an electrically actuatable variable-ratio transformer (Variac) between the power line and the input of the power supply. However, the cost and complexities associated with such an approach would be unacceptably high in most applications.
Or, one might consider the use of a Triac-type voltage control means mounted between the power line and the power supply. However, Triac-type voltage control means simply do not function properly with the kind of input characteristics normally associated with power-line-operated inverter-type power supplies.
Then, there is the possibility of using an inverter-type power supply with a special input circuit that would permit the use of a Triac-type control means; which input circuit would then have to make the inverter power-input-characteristics appear substantially like a resistive load. Even so, however, there is the cost and the electrical inefficiency of the Triac-type control to consider.
The present invention represents yet another solution; which other solution is novel, less costly and electrically more efficient than that of using a Triac-type control means between the power line and the inverter input.